The assignee of the present invention designs and manufactures spacecraft for communications and broadcast services. Electrical power for such spacecraft is conventionally generated by photovoltaic solar arrays, typically having several thousands of solar cells.
Solar cells of numerous varieties are known, but typical features of the types of cells with which the present inventors are concerned, are illustrated in FIG. 1. Referring to Detail A of FIG. 1, cell 100 has a semiconductor substrate 110 having a base region or layer (“P-side”) 112 formed of a first conductivity type below or behind an emitter region or layer (“N-side”) 114 of opposite conductivity type. A metallized conductor on the back surface of the P-side forms a first electrode (“back contact”) will. A grid on the front surface of the emitter region, which surface is the light receiving surface, forms a second electrode (“front contact”). The grid, typically composed of fine metallic lines 130, is conductively coupled to at least one current collector bar 140. For improved packing densities, cells having a substantially square or rectangular footprint are preferable. Referring to detail (B), a substantially square solar cell 100 may be formed from a substantially circular wafer 170. Alternatively, two similarly sized substantially rectangular cells 100a and 100b may be formed from the circular wafer 170. It may be observed that the resulting square or rectangular solar cell may have one or more relatively short corner edge segments 150 disposed at an obtuse angle to main side edges 160.
Referring now to Detail C, in order to connect an electrical series (or “string”) of solar cells, one or more cell interconnects 126 may be disposed between adjacent cells 100 that conductively couple the back surface electrode 120 of one cell 100(i) to the current collector bar 140 disposed in a front surface of adjacent cell 100(i−1) in the string.
As the demand for higher power spacecraft has grown, so has the demand for higher power solar arrays, each array typically consisting of two or more solar panels, with a consequent requirement to arrange even higher numbers of solar cells on each solar panel. This in turn places an increased emphasis on improving the ratio of solar cell area to solar panel area (hereinafter, “the panel packing ratio”) and in achieving increased reliability and cost efficiencies in making the necessary electrical connections between cells.
In light of the foregoing, solar cell configurations, whether for space or for ground applications, that permit improvements in the above mentioned metrics, are desirable.